The Austrian patent publications 344,963 and 350,237 disclose extruded ceramic exterior wall tiles for mounting with their long sides axis upright and having vertical, rectangular rounded holes, and which have U-shaped recesses at the marginal surfaces, which to the front and to the rear are delimited by the front and rear projecting tile part and in the middle or internal part are delimited by a web connecting said parts together. The head and foot marginal surfaces, which are interrupted by the holes, are essentially constituted by a simple straight cut which is perpendicular to the surface of the tile.
The disadvantages of such exterior tiles are to be more particularly seen in the fact that lateral cutting to size, frequently necessary during mounting the tiles, is not possible in a manner which is satisfactory both technically and aesthetically. Thus if an exterior wall tile is cut down to size at the side, that is to say parallel to the holes, the cut will as a rule not extend through one of a few narrow webs, but rather through one of the holes. Frequently the remaining front and rear tile parts will extend far past the two webs connecting the two parts so that the resistance of the exterior wall tile to fracture is substantially reduced. If such exterior tiles are installed with vertical spacing gaps, the small thickness of the material will be full disclosed, something undesired from the architectonic point of view. This will also be the case if--as with a tile not cut to size--the front and rear tile parts only project laterally to a slight extent and the resistance to fracture for such parts is insufficient, Further drawbacks of such exterior tiles are that the laterally projecting tile parts connecting webs and the lateral connecting webs cause a considerable braking effect on the ceramic material during extrusion and accordingly an insufficient compaction of the material. This in turn leads to an increased proneness to dry cracking, increased rates of dry breakage end a reduced resistance to fracture of the fired exterior tiles. These disadvantages are furthermore also accelerated because the marginal drying of the tiles is still further increased by the increased surface area here so that the speed of drying of the tile body is even more advanced than in a normal case.
A further drawback of such extruded exterior tiles is to be seen in the fact that owing to their straight cuts at the head and foot no satisfactory conduction or draining of water is ensured. This is more particularly significant if the exterior tiles are installed with horizontal spacing gaps, through which water on the wall and beating rain may penetrate and which also permit unobstructed viewing through as far as the supporting structure behind the tiles.
The German patent publication 3,110,606 C discloses extruded exterior tiles with round or oval holes and simple or undercut grooves, which are respectively arranged in the direction of extrusion. Exterior tiles are, to the extent that they are to be attached with their long sides horizontal, provided with an extruded hole and foot interlocking ledges for the purpose of draining away water and improving the appearance of the joins.
The tiles mounted with their long sides vertical are cut straight at the sides, that is to say perpendicularly to the holes, so that in this case a stapless horizontal adaptation to size is readily possible by cutting the exterior tiles. Should exterior tiles be installed with their long sides vertical, then they will be cut straight at the top and bottom so that poor water draining and a gaping space between the tiles will have to be tolerated. On the other hand however vertical adaptation to size is simple, because it is possible by straight cutting of the tiles. The substantial drawbacks of such exterior tiles are that stepless adaptation of the exterior tiles perpendicularly to the direction of extrusion is not possible, since then cuts as a rule extend either parallel through the holes or parallel through the grooves so that the resistance to fracture of the tiles is substantially reduced. The wall thickness, which is reduced at the positions of cutting through the holes or grooves will then be betrayed to the eye owing to open spaces between tiles. A further disadvantage of such exterior tiles is that the proportion of holes and grooves is very low with the result that their weight is relatively high. The consequence of this is that such tiles take a long time to dry during manufacture, are prone to become bent while soft and there is a high fracture rate during drying and firing. Furthermore, the supporting bracket structure necessary for installation of the tiles has to support a greater load.
Further extruded exterior tiles are disclosed in the German patent publication 3,401,271 C. They are arranged with their long sides vertical and are provided with square holes. The front and rear tile parts are connected by narrow webs extending between the holes and at the tile edge. These exterior tiles may be attached with the long sides vertical, but then with the disadvantage that owing to the straight cut transversely in relation to the holes there is poor drainage and there are gaping spaces left between the tiles. A particular drawback is however furthermore to be seen in the impossibility of stepless size adaptation transversely to the holes, since the cuts parallel to the holes which are necessary generally intersect the holes. In the case of attachment of the tiles with the long sides horizontal there is an increased chance of fracture of the downwardly over-lapping front tile part. The thinner tile portion becoming visible in the space or gap is accepted by the eye as a draining or drip sill in the case of tiles with the long sides vertical but not if they are horizontal.
A further drawback of such exterior wall tiles is to be seen in the complex configuration at the top and bottom edges due to the head and foot ledges, which as described above owing to an increased surface area and low wall thickness leads to a poor flow of the plastic ceramic material during extrusion, to excessively rapid drying at the edges and consequently to increased breakage rates and to greater lability to fracture.
One object of the invention is accordingly to provide an extruded, more particularly ceramic, exterior wall tile, which has a relatively low weight, renders possible a good stepless adaptation to size in a direction across the direction of the holes without even a single cut through one of the holes or grooves being necessary, and which furthermore ensures satisfactory drainage and is also simple and economic to produce.